For characteristics like small volume, low power consumption, free of radiation, etc., Thin Film Transistor Liquid Crystal Display (TFT-LCD) technology has developed rapidly in recent years and has become prevalent in current flat-panel displays. At present, the TFT-LCD technology is widely used in various sized products including small, medium, and large products, covering a broad spectrum of modern electronic products, such as a liquid crystal television, a high-definition digital television, a computer (desktop and laptop), a cell phone, a tablet, a GPS, a vehicle-mounted display, a projection display, a video camera, a digital camera, an electronic watch, a calculator, an electronic instrument, a meter, a public display, a virtual display, and so on.
At present, a production line of a TFT-LCD display panel is divided into four main working sections, i.e., Array, Color Filter (CF), Cell, and Module.
The Array section relates to the manufacture of a TFT array substrate, having a focus on the manufacture of signal lines of metal layers and individual pixel capacitor units on the TFT array substrate.
The CF section relates to the manufacture of a Black Matrix (BM) layer, an RGB layer, a transparent electrically conductive layer, etc. on the CF substrate.
The Cell section relates to adhering the TFT array substrate and the CF substrate to one another by using a seal to form an integrated and closed panel (liquid crystal screen), which mainly includes the steps of printing a rubbing film, aligning the rubbing film, dripping liquid crystal, curing with the seal, etc. In the Cell section, after a large glass substrate (motherboard glass) is fittingly adhered, it is cut to result in smaller pieces of liquid crystal screen units, and then a Cell Test is performed for the liquid crystal screen units. The Cell Test aims at detecting defects, which mainly include mura, block, cell stain, bright line, and so on, of the liquid crystal screen units appearing in the Array and Cell sections. Generally, the display panel needs to be provided with a panel function test circuit for the Cell Test.
The Module section mainly includes assembling the manufactured liquid crystal screen units, on which a polarizer and a PCB drive circuit have been affixed, with a backlight to form a final finished display module product.
When the display panel works normally, a phenomenon of Electrostatic Discharge also exists. Electrostatic Discharge is a major factor in causing electronic assemblies and electronic systems to suffer Electrical Overstress damage, which may lead to permanent destruction of semiconductor devices, thus resulting in functional failure of the integrated circuit. Therefore, the display panel further needs to be provided with an electrostatic protection circuit for use during operation of the display panel, wherein the electrostatic protection circuit often connects electrically with a signal line of the display panel.
Since both a panel function test circuit and an electrostatic protection circuit need to be provided, respectively, more wiring space is required.